The 3.8.0 league was Blight, in which we assist Sister Cassia, an exiled inventor in stopping the spread of the “Blights”. This takes the form of a quick tower defense event, in which you can create towers to slow the advances of monsters, while you use your own skills to kill them, before they reach the central pump, which is draining oils from the Blight. As a reward, you will receive the extracted oils that allow for unique enchantments, as well as a variety of other rewards.
As of 3.9.0, Cassia is encountered roughly one in every ten maps, with a change to the rewards, at least one oil or Blighted map dropping from every encounter.
Enemies will spawn from a number of nodes (visible at the bottom of your screen as the Blight begins to spawn) and will travel along predetermined paths towards the central Blight, where they will begin to destroy it. If it is destroyed, any rewards from monsters slain will still be awarded, and any spawn points you exhausted of enemies will be lootable. Tower locations will pop up as you go, and you can build and upgrade your towers at these locations, as long as you have the resources for it, which are replenished by defeating monsters. The majority of monsters will not attack you if you stay off the lanes, but if you get in their way, they pack a serious punch, so be aware of where you are standing!
Builds capable of dealing damage at locations away from themselves, such as minion builds, cold damage over time builds, or totem builds, are excellent choices for engaging with the Blight mechanic.
There are six types of towers in the league, each with their own uses and benefits to consider. Generally speaking, if you are more powerful than the content you are dealing with, you do not need to worry much about tower strategies. However, if you are struggling to keep up with the monsters, the towers are there to help. Each tower has four tiers, with the fourth being a choice between one of two paths to upgrade along. Each upgrade has its own uses, and every tier of tower improves its effects, range, or damage.
The progress chart at the bottom of the screen will show a number of circles equal to the number of paths that will spawn, and each of those paths can have a variety of symbols. Most important among them are the symbols denoting resistances, so look out for these and keep them in mind when building a tower. The flame denotes resistance to Fireball towers, the snowflake to Chilling towers, and so on.
This is the simplest tower. If you are lacking damage, it will be your best friend! While it cannot solo a blight for you, when placed near a cluster of Blight paths, it will significantly boost your damage output. At rank four, you have a choice between an extremely long range Meteor tower, and a Flamethrower tower. The Flamethrower will provide excellent damage if it can fire along a path, so if you are struggling to keep up in terms of damage, this is likely your best choice. If your tower is positioned more awkwardly, upgrading to the meteor tower is a much better option.
As a general rule, the Meteor tower is the strongest tower when focusing on Blighted maps, so anointments for it are the best performers.
The chilling tower, as its name suggests, chills nearby enemies. It functions similarly to 
Siphoning Trap, sending out slowing beams. It is great at giving you much needed time to move between paths, and can boost your damage if you are using certain items that provide bonuses against chilled enemies. At rank four, you are given a choice between the Glacial Cage and Freezebolt towers. The Glacial Cage tower casts a circular 
Frost Wall style effect around enemies, impeding their movement greatly. This is a great crowd control ability, especially when you see unique monsters popping up. The Freezebolt tower casts a long range spell that deals high damage and appears to have a decent chance to freeze enemies in their tracks. It also pierces, and thus offers a good balance between crowd control and damage. Like the Flamethrower tower, the Freezebolt tower will perform best at the end of a long straightaway, so keep your positioning in mind when upgrading this tower.
The Shock Nova Tower casts a small Shock Nova style spell, with the range and damage increasing as it levels. More important than the damage, however, is the fact that it drops shocked ground. This provides a decent boost to damage, and can shock a decent number of monsters if placed in a bend in a path. At rank four, you have the choice between Lightning Storm tower and Arc tower. The Lightning Storm tower calls down lightning around itself, dealing damage in a very wide area, offering a decent boost to your clearing potential. The Arc tower, as its name suggests, casts Arc at nearby enemies, with a high chance to shock, once again dealing respectable damage over a large area.
The Seismic tower sends out a series of shockwaves, with low damage and guaranteed stuns. Anywhere you can overlap with several paths, it will provide great value to any Blight defense. At rank four, it offers the choice between Temporal tower and Stone Gaze tower. Temporal tower creates bubbles of slowed time for enemies, slowing massive areas at once. The Stone Gaze tower functions much like the basilisk attack. It links to several enemies and gradually slows them to a halt, allowing you to take your time to finish them off. If you are struggling to keep up with paths in several directions, the long range slows from this tower are a great help.
The Summoning tower brings in reinforcements, slowing enemies simply by getting in their way. They deal a bit of damage, and as you upgrade your tower, you will get more minions, all of which can block different paths. At rank four, you are offered a choice between Sentinel and Scout towers. The Sentinel tower offers a single, very bulky minion, useful for blocking particularly dangerous enemies. Scout towers will summon ten flying minions, which attack with powerful lasers, dealing quite high damage. These make a respectable option for augmenting your damage in difficult encounters, and can potentially carry you through even difficult Blighted maps.
At rank one to three, the Empowering tower projects an aura that simply boosts your other towers, growing in radius with each level. At fourth level, you can upgrade to Smothering or Imbuing towers. The Smothering tower weakens enemies, though it is somewhat unclear what this means, specifically. The Imbuing tower provides players with increased speed, which can be crucial in difficult Blights. Overall, these towers provide amazing power, but are largely not worth using prior to more difficult blights, like those in Blighted maps.
Twelve oils were introduced with the league, with varying rarities. They can be vendored together, with three of one tier vendoring into a single higher tier oil. They come from successful Blight encounters, and offer one of the most unique and powerful rewards of the league: Amulet and Ring enchantments! These enchantments are determined by the type and number of oils placed in the enchanting device, and on amulets they provide access to notable passives on the tree. This means that a combination of three oils will always grant the same notable, and you can get access to powerful defensive and offensive notables for your build if you know what to look for.
In addition to the notables on the passive tree, thirteen secret notables are available through oil enchanting, including Cleansed Thought, which doubles your chaos resistance, and Vengeant Cascade, which allows your projectiles to return to you from their final target, piercing all enemies on their way back.
On rings, the oil enchantments grant powerful bonuses to your towers, allowing you to specialize, such as granting extra projectiles to your fireball towers, or extra area to chilling towers. Meteor, Scout, and Chilling towers offer the best bang for your buck, so enchantments for them are your general best bet. If you prefer other towers, however, any can perform well with their respective enchantments.
There is a list of all available notable passive skills here, so if you are looking for a specific notable, search it on this table. More powerful notables, like Soul of Steel or Whispers of Doom are, unsurprisingly, demanding in their oil costs, though there are many powerful options available for quite cheap.
In addition to oils, Blight encounters can also drop new Blighted maps. These maps have no native monsters, instead being jammed full of Blights, bigger and more numerous than in any other content. These can offer loads of oil, as well as other great rewards, so keep an eye out for these maps as you enter the endgame. It is highly recommended that you avoid mods that make monsters much tougher to kill. Mods that affect unique bosses will affect any unique monsters that spawn in the map, so be careful if you are running maps with double boss.
These maps take everything you know about Blights and crank them up to eleven, with a huge number of paths, and tons of towers to manage. The default recommended strategy is to build crowd control towers as fast as possible, and upgrade them as you are able to. If you can bring a friend along, it will be a great help, even if one of you is focusing on building towers while the other focuses on taking out monsters.
As the Blight progresses in these maps, they will start to draw in monsters from several directions at once, so keep an eye on your map to know when you need to move to kill on other paths. These maps can also be annointed, adding a variety of unique modifiers, including extra experience and significant boosts to rewards. These are all viewable in the list of anointments above.
The easiest, and most consistent strategy, from testing, has been to stack up many of the same damaging towers, and clean up survivors yourself. This is particularly good if your build lacks the ability to deal damage over long ranges, or in multiple places at once. Meteor and Scout towers are the most consistent for this strategy, and will clear well over half the monsters in a map before they get near the pump, leaving you an easy task of cleaning up the rest.
If you are playing a build that can take deal with further enemies, building Chilling and Seismic towers, and upgrading them to Glacial Cage and Temporal towers on chokepoints can be a great strategy. As mentioned below, this can cause issues of extreme lag, and is no more consistent than building for pure damage in most cases. Summoners, totem builds, and bow builds can utilize this strategy the most effectively, especially because Glacial Cages can make it hard to damage enemies inside of itself.
In general, the first three tiers of oils, Clear, Sepia, and Amber oils are the best choices if you are struggling to keep up with the difficulty of monsters. Stacking several of these will make the difficulty drastically lower, allowing a lot more lenience. Amber oils make towers much cheaper, so you can slam down towers faster and more easily, while Sepia makes them deal more damage. The weakest of the three, Clear oils slow enemies. All three of them offer 5% increased monster pack size, a fairly small boost that is shared by most oils.
If you are confident in your chances of success, Teal and Crimson oils offer the best bang for your buck, increasing pack size a bit and making several of your chests lucky. While it is unclear exactly what this does, numerically, it is clear from the experience of many players that they are a significant boon. Silver oils offer even more benefits, but are generally not worth the expense, with the potential exception of already extremely expensive high tier maps.
When rolling the maps themselves, look to minimize enemy defenses and speed, as these are the things that increase the difficulty of Blighted maps the most. High pack size is nice, especially if you are aiming for experience gains, but the bulk of your rewards come from chests.
While there have been numerous fixes to improve this, Blighted maps can still cause performance problems, especially on lower-end machines. This can cause serious problems, even leading to instance crashes in the most extreme cases. In order to avoid this, and reap the rewards from your hard fought content, you will want to work on reducing the lag caused in the instance. There are a few ways to do this, and hopefully you will not need to know how to do this for long, as there are expected to be patches coming soon to help alleviate these issues.
The most important lag reduction method is to avoid stacking monsters. Too many monsters in a single place results in lag spikes, and eventually a disconnect, if you do not deal with them. To avoid this, do not place your crowd control towers near the edges of the map, instead positioning them closer to the pump. This will allow you to more efficiently clear out monsters as you are running back and forth between spawn locations. In keeping with this advice, it is best to always be killing monsters.
There are a few specific towers and positionings to avoid, in order to reduce lag buildup. When stacked, the Stone Gaze tower’s petrifying ability can cause serious issues, potentially leading to monsters becoming permanently frozen, so avoid overlapping their area of effect, opting instead to only build one or two. Similarly, the Glacial Cage tower should be kept near the Blight pump, as placing them near the start of the paths is one of the easiest ways to get huge, lag-inducing stacks of monsters. When placed near the end, they are still great for catching any monsters that have made it past you, but will not present the same lag issues.
Patrick has been playing PoE since Closed Beta in 2011. He creates PoE guides, focusing on League Mechanics, as well as videos talking about PoE. You can find his content primarily on his YouTube channel and follow him on Twitter If you have any questions about his guides, please join the PoE Vault Discord.
